Vintage Cars: oil pressure guage nut, oil pressure guage, oil drip

Question
QUESTION: 1980 240 diesel Mercedes dripping oil from behind speedometer panel. what can cause this and what oil line would be attached to that panel?

ANSWER: that is from your oil pressure guage, you may be able to open the deck under the dash and tighten,should be an 8 or 10mm nut, be careful not to overtighten, and do not ignore it  as you amy end up with a sudden loss of oil pressure
Good Luck

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QUESTION: The oil pressure guage nut under the dash in my 1980 240 diesel Mercedes looks to have a smaller nut on top of a bigger nut. Is there a specific way this should be tighten to stop an oil drip?

Answer
the larger nuts holds the guage in place and is used to counter act the tightening of the smaller nut.  In other words, turn the smaller nut into the larger , hold the larger in one place, again do not attempt to overtighten or you will have a mess! tighten till good and snug